1. Field of the Invention
The present invention relates to a modular direct fuel cell system having an integrated processor.
2. Description of the Related Art
A fuel cell generates electricity through an electrochemical reaction between hydrogen and oxygen supplied by external fuel. Typical reactants used in a fuel cell are hydrogen on an anode side and oxygen on a cathode side. Because the only by-product of a fuel cell is water vapor, such fuel cells are desirable for their high efficiency and essentially emission-free use.
Fuel cells are generally classified according to the types of electrolytes they use. Some fuel cell are useful for a stationary power generation facility, and other fuel cells are useful for small mobile devices or for powering cars.
A direct methanol fuel cell (DMFC) relies on the oxidation of methanol on a catalyst layer to form carbon dioxide. Water is consumed on an anode and is produced on a cathode of the DMFC. Protons H+ are transported across a proton exchange membrane to the cathode where the protons react with oxygen to produce water. Electrons are transported via an external circuit from the anode to the cathode that supplies power to an external apparatus. DMFCs do not use a reformer to extract hydrogen from a fuel, which allows the DMFCs to have a compact design, e.g. for use in a mobile telephone.
More specifically, a DMFC includes an anode, a cathode, and an electrolyte membrane between the anode and the cathode. An aqueous methanol solution is used as fuel. A fuel supply source is connected to the DMFC to supply fuel to the anode and an air supply source supplies air to the cathode. A heat exchanger is connected to a cathode exhaust stream to cool the exhaust stream, condense water from the exhaust stream, and discharge the condensed water to be mixed with the fuel. The condensed water is re-circulated to the fuel supply source to be re-used. It is not necessary to premix the fuel with water, thereby allowing the size of the DMFC to be reduced.
A function of a DMFC system is the separation of CO2 from a stream including a mixture of methanol, water, and CO2 discharged from a fuel outlet of a stack. In order for the DMFC to function properly, CO2 must be separated from the stream prior to re-circulating the stream back to the stack. A DMFC system of this kind has been disclosed in U.S. Pat. No. 6,110,613 and U.S. Patent Publication No. 20040062964. The latter discloses condensing water in a heat exchanger of a DMFC system to separate the water from an exhaust stream of the DMFC system, re-circulating the water, and mixing the water with a fuel.
A CO2/fuel separator is installed downstream of a fuel outlet of a stack. An anode cycle for fuel mixture, which includes the CO2/fuel separator, removes CO2 from a reaction stream and exhausts CO2 to the atmosphere through an exhaust outlet. In a fuel mixer, the fuel mixture stream, from which CO2 is removed, is mixed with concentrated fuel received from a fuel tank. A fuel pump feeds the fuel mixture back to the fuel inlet of the stack.
Generally, a DMFC system has many fluid connections between different components, and these fluid connections cause difficulty in manufacturing the DMFC system. More specifically, the assembly of many fluid connections can cause difficulty in automation due to the complex geometrical shapes of the components. In addition, leakage and mix-up of the fluid connections can lead to degradation in quality of the DMFC system. Further, the conventional DMFC system may have an increased number of fluid connections due to the numerous modular components.